In elevators provided with automatic doors, the landing door is generally moved by the car door. The coupling between the car door and the landing door is implemented using a door coupler which is mounted on the car door and engages counterparts mounted on the landing door by means of its gripping elements. The door coupler and the counterparts are so fitted relative to each other that, when the elevator car is moving past the landing door, the counterparts on the landing door are passed between the gripping elements of the door coupler. When the car is at a landing and the car doors are moving, the door coupler is in engagement with the counterparts. In this way, the landing door also moves when the car door is moved by a power means connected to the car door. Often the gripping elements are metal vanes projecting from the door coupler towards the landing door and forming a kind of a vertical slot which is open towards the landing door. The counterparts used often consist of rollers mounted on the landing door and projecting from the door towards the elevator shaft, the axle of the rollers being mounted in a position perpendicular to the plane of the door.
When an elevator car stops at a landing, usually the elevator car and the landing devices are not exactly aligned with each other, but either the location or position, or both, of the elevator car differs at least somewhat from the ideal location or position with respect to the equipment at the landing. For this reason, there are problems with the coupling between the car door and landing door, because inadequate ligament between the door coupler and the counterparts may lead to a host of various problems. If the door coupler is not properly aligned with the rollers on the landing door, this may result in noise, reliability problems, interruption of door operation, obstruction of emergency opening of the door, incomplete opening or closing movement of the door, etc.